Integration of Fiber Optics and Free Space Optics: A Hybrid Approach for Last Mile Connectivity

As a result of the humongous boost in the number of ultra-speed applications, the current network infrastructure is not adequate to provide sufficient data rates and bandwidth. As a result, radio frequency (RF) and microwave-based links are facing the problem of spectrum congestion and consequently, optical fibers have emerged as an efficient candidate to overcome the bandwidth constraints of last-mile users. But it is not feasible to install and deploy fiber-based networks in remote locations and areas having difficult terrains along with other geographical constraints. Hence, we can integrate the optical fiber-based system with free space optical (FSO) links in such scenarios for ensuring high-speed data services for the users. In this work, we are proposing a wavelength division multiplexing (WDM) based 8-channel hybrid fiber-optics/FSO system to remove the bottleneck problem for the end-users in the existing network infrastructure. The proposed hybrid system is capable of serving 32 optical network units (ONUs) by incorporating a single mode fiber (SMF) of 20 km along with FSO link range varying from 0 to 2 km. In addition to this, the system performance has been inspected under light, moderate, and heavy fog scenarios. It has been found that the hybrid optical system is capable of transmitting data successfully for the FSO link distance of 1 km under light fog weather conditions only. The maximum attainable FSO link range for delivering a target bit error rate of $10^{-8}$ drops by 41.07% as the FSO channel conditions change from light to heavy fog.